Here's what you need to do to find the mass of a compound from a chemical equation:
1. Balance the equation: Make sure the number of atoms of each element is the same on both sides of the equation. This ensures the reaction follows the law of conservation of mass.
2. Identify the compound of interest: Which compound in the equation do you want to find the mass of?
3. Determine the molar mass of the compound: This is the mass of one mole of the compound. You can find this by adding up the atomic masses of all the atoms in the compound's formula.
4. Use stoichiometry to relate the moles of the compound to the moles of other substances in the reaction: This is done using the coefficients in the balanced equation. For example, if the equation shows 2 moles of A reacting to form 1 mole of B, then the mole ratio of A to B is 2:1.
5. Convert moles to grams: Once you know the moles of the compound, you can multiply by its molar mass to get the mass in grams.
예 :
Let's say you have the following balanced equation:
2 h→ + o₂ → 2 h₂o
You want to find the mass of water (H₂O) produced when 4 grams of hydrogen (H₂) react.
Here's how you would solve it:
1. Balanced equation: The equation is already balanced.
2. Compound of interest: h₂o
3. Molar mass of H₂O: 2(1.01 g/mol) + 16.00 g/mol =18.02 g/mol
4. Stoichiometry: The mole ratio of H₂ to H₂O is 2:2, which simplifies to 1:1. This means for every 1 mole of H₂ consumed, 1 mole of H₂O is produced.
5. Moles of H₂: Divide the mass of H₂ by its molar mass:4 g / 2.02 g/mol =1.98 moles of H₂
6. Moles of H₂O: Since the mole ratio is 1:1, you also have 1.98 moles of H₂O.
7. Mass of H₂O: Multiply the moles of H₂O by its molar mass:1.98 moles * 18.02 g/mol =35.7 g of H₂O
Therefore, 35.7 grams of water are produced when 4 grams of hydrogen react.
중요한 메모 :
* You need to know the mass of at least one reactant or product to calculate the mass of another substance.
* The actual mass of a compound produced in a reaction can be affected by factors like limiting reactants and reaction efficiency.
